I have been interested in sites that offer interactive applets or scripts to show chess problems. Some offer mainly tactical puzzles and others mainly chess compositions. Below is a collection of such sites with my brief comments.

(1) http://chessy.freehostia.com/Mainly 2- and 3-move compositions.Board itself is not interactive. Solver writes the key into a provided textfield and gets feedback on correctness. Also possibility of commenting on problems. The site keeps tally on results. Used to have a forum, which is (temporarily?) out-of-order. Currently contains 140 problems of varying difficulty. No tactical puzzles.

(2) http://www.chessproblems.com/A very nice site with 1400 problems. Mixed compositions and tactical puzzles are set by the (currently over 2100) registered users of the site. Hence they vary greatly on quality and difficulty.The Java board is interactive and excellent in design. Only for the problems with mate in >3 the applet is too slow for us humans :).The problem building applet is the best I have seen and very intuitive. There is also a forum associated.

(3) http://www.chessworld.net/chessclubs/fo ... tegoryid=1Although www.chessworld.net is mainly targeted for playing of e-mail games between the members (over 400 000), there is a large interactive puzzle base (current last puzzle number is 1684).The puzzles divide into three cathegories compositions, endgame studies and middlegame tactics as apparent from the link. There are corresponding forums as well.The applet for interactively solve the problems is javascript/asp based construct shown in an <iframe>- element. If user makes a wrong move, it will just pop-up "Wrong move"-message box cand keep count of these errors.

(4) http://chesstempo.com/Is a relatively new site (a few months) that offers interactive applet mainly (solely?) for tactical puzzles. You solve the applet selected puzzles one after another and get a rating in 'blitz' (with solving time considered) or 'standart' (No time element) solving ability.Site keeps a list of best tacticians and has a forum, too.

(5) http://chess.emrald.net/Is very similar to above, but much older. Probably a kind of 'role model' for the above newer site.There are over 20 000 tactical problems and over 2000 registered and ranked tacticians on the site.A sort of messageboard included.

(6) http://satiriki.ru/chess/english/index.htmlFrom Alekhinechess.com this site offers you a choice to interactively solve >1000 problems, >200 studies or >600 tactical exercices. As a specialty you can select number of moves and number of pieces and difficulty level for problems. for studies and tacticals only difficulty level (from 1...6) is selectable.

(7) http://www.enpassant.dk/chess/problems/problemsuk.htmHere is a collection of 300 combinations on 25 pages. Some are easy, some are difficult and some are very difficult! There is also a collection of 89 endgame studies by the Platov brothers.All problem pages are HTML/JavaScript made with Palview. You can try to find the right solution 3 times before it is revealed. Making a move/guess is simple: just click on the piece you want to move and then click the target square.

(9) http://www.chess-poster.com/chess_probl ... oblems.htmThere are 30 endgame exercises you can interactively 'solve'. The interesting feature is that you will be playing against Lokasoft's 'Little Chess Partner' Java-applet and the play may take quite different outlook from intended solution. I guess, if you win the applet, you have 'solved' the problem!

(10) http://www.chess.com/forum/category/daily-puzzlesChess.com is a relatively new, busy site with approximately 70 tactical puzzles (of the day) are set currently - and the amount growing daily. The site is basically a forum with solvers commenting set puzzles. For each move you get feedback (Correct/wrong), but no ranking of members is done (so far).

(11) http://www.bertvandermarel.nl/mastermove/index.htmlAs the name says this site belongs to Bert van der Marel. It contains about 200 endgame studies by famous composers. The special feature is the 'Guess the move'- action, which pops out during the solution process. You will be awarded points for correct moves. Most of the interactive studies are in the archive. It appears that the latest is from Jan 2006.

(12) http://www.mrmip.net/mipsofacto/index.htmLast - but not nearly least - comes my own site with the famous QuizzoFacto(R) -engine. This engine is written by purely client-side javascript and will automatically solve one- or two-move problems.(too slow for longer problems). I have put some 150 such problems on the site. The specialty of the script is that it will force the solver to walk through all variations of a problem. It will also evaluate solver's 'rating' for these problems. I am currently seeking for a way to handle longer puzzles.

(13) http://www.chess-problems.org/en/lessons/Site contains more then a hundred of chess tactical positions, which are chained by complexity. All compositions accessible by interactive tool, which helps to check the solution. All solved solutions are stored in the user's profile. It will be very useful for chess starters.